Employee Benefit Plans - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ 41,600,000	$ (43,900,000)	$ 74,300,000
Accumulated benefit obligations	1,500,000,000	1,600,000,000
Contribution plan expense	12,500,000	15,900,000	6,000,000
Reserves for incentive plans	16,400,000	13,600,000
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	52,700,000	458,300,000
Accumulated benefit obligations	1,478,100,000	1,585,200,000	$ 2,132,900,000
Employer contributions	17,800,000	13,000,000
Expected future contribution	7,700,000
Pension benefits | United States
Defined Benefit Plan Disclosure [Line Items]
Expected future contribution	0
Other various benefit plans
Defined Benefit Plan Disclosure [Line Items]
Noncurrent postemployment benefits liability	$ 1,000,000	$ 1,900,000
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations	90.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations	10.00%